Differential driving mechanism



June 14, 1960 G. M. coANET 2,940,340

DIFFERENTIAL DRIVING MECHANISM Filed July 17, 1957 4 Sheets-Sheet 1 Fig..7

.2' xm l l* HY June 14, 1960 G. M. COANET 2,940,340

DIFFERENTIAL DRIVING MECHANISM Filed July `1'7, 1957 4 Sheets-Sheet 2June 14, 1960 G. M. coANET DIFFERENTIAL DRIVING MECHANISM Filed July 17,1957 4 -Sheets-Sheet 3 n 0 l 2, A 6 f Fig. 72

Fig. 73

lill/III June 14, 1960 G. M. coANE'r 2,940,340

DIFFERENTIAL DRIVING MECHANISM Filed July 1'?, 195'? 4 Sheets-Sheet 4United States Patent IOmce 2,940,340 Patented June 14, 1960 2,940,340DIFFERENTIAL DRP/'ENG MECHANISM Guy Michel Coanet, Paris, France,assignor to Compagnie des Machines Bull (Societe Anonyme), Paris, FranceFiled July 17, 1957, Ser. No.l 672,394

Claims priority, application France July 17, 1956 4 Claims. (Cl.74i-757) In computing machines and accounting or statistical machinescontrolled by record cards or tapes, it is sometimes necessary forensuring correct operation of certain parts of the machine to adjustdifferently the instant of operation of some parts, depending upon therequired speed of operation of the machine. These diierences inadjustment have the object of compensating for the effects of inertiadeveloped during the starting or stopping of the controlled parts. It issometimes also necessary to make some readjustments for compensating forthe variations in the mechanical strength of parts which have becomeharder or freer after someperiod of operation. Particularly greatdiculties arisein correctly adjusting mechanisms having a variable load,.such as accumulators of accounting'machines in which carry-overmechanisms may be actuated at different instants during the operation ofthe accumulators. The influence ofthe variable loads of the inertiaeffects and of the variations in the passive resistances may be reducedby introducing into the mechanisms permanent. resistances (frictionmeans or pawls for braking) butv these resistances increase the load onthe transmissions, the noise and the wear on the mechanisms. Thesedisadvantages are obviated by providing driving devices in thesingle-turn clutches of the type currently employed inY accountingmachines. These devices ensure accurate starting and stopping of themechanism in a clearly determined angular position independently of theload of the mechanism and of the speed of operation of the machine. Forexample, French Patent No. 527,463. applied for on July 2, 1920, isknown, which relatesto a computing machine in which the wheels of theVaccumulators are driven by diiferential mechanisms each comprising twobevel gears, one of which is coupled with a totalling wheel, and inwhich the starting and stopping of each totalling wheel is controlled bythe actuation of an escapement mechanism which locks one of the bevelgears. In such a device, the escapement mechanism passes by anintermediate position in which the pawls of the escapement are inengagement with the two bevel gears of the differential simultaneously,which may cause deterioration of the mechanism. Moreover, in thismechanism the escapement must be maintained in its active positionthroughout the duration of the driving of a wheel of the accumulator.

The present invention has as its objectV to obviate these disadvantagesand to provide a device which can be used for driving a mechanism andthe stopping thereof in predetermined angular positions, while thedriven mechanisrn can oppose within certain limits variable loads in thecourse of the operation and can be used at different speeds of thedriving shaft of the machine.

One object of the invention is to provide a differential drivingmechanism comprising a driving shaft, one or more planet wheelsmechanically coupled with the said driving shaft, two bevel gears freelymounted on the planet wheel or wheels, so that one bevel gear,mechanically coupled with the mechanism to be driven, is driven by therotation of the said shaft when the other bevel gear is locked, lockingteeth on each bevel gear wheel, a control member arranged to occupy twoactive positions for the locking ofv one or other of the said bevelgears, the said member comprising opposite each of the said sets oflocking teeth a locking pawl, the arrangement being such that when onepawl locks one bevel gear the other pawl releases the other bevel gear,and the said mechanism beingrcharacterised by the fact that there isprovidedan intermediate position of the control member, in which theVtwo pawls are simultaneously disengaged from the said teeth, land inthat there is provided an aux,-

locking device consisting oftwo locking members each cooperating withthe locking 'teeth of one bevel gear. The said locking members arerigidly. connected together and sordisplaceable that, when a lockingmember is maintained out of engagement with the locking teethV of onebevel gear as a result of the rotation of the latter, the other lockingmember is maintained in engagement with the locking teeth of the otherbevel gear and maintain -it in the locked position.

Y The starting or stopping of a mechanism with a device designed inaccordance with the inventionmay be controlled by impulses and affordsgreat iiexibility and safety of operation, obviating any danger ofdeterioration of the mechanism.

Various embodiments of the invention and features thereof willvbel shownyby way of example in the course of the following description.V `andwith reference to the accompanying drawings, in which:

Figure l is= a diagrammatic View of a driving device designed inaccordance with the invention, partly in section along theline l-l ofFigure 2,

Figure 2 is arsection along the line 2 2 of Figure l,

Figure 3 is a view of thecontrol member actuated by an electromagnet,

lFigure 4 is a view of the control member actuated, by an electromagnetdifferent from that of Figure,

Figures 5 tol() are diagrammatic views of the auxiliary locking devicein diiierentY positions,

Figure ll is a diagrammatic view of a modified em: bodiment,

Figure 12 is a transversesection through an accumuf latorv along theline 12,--12 of Figure14,

Figure 1.3 is a, side view of the accumulatorV of Fig: ure l2,

Figure 14 is a fragmentary plan view of the aceumuf lator according toFigure l2 as seen in the direction of the arrows 14-14 with some of thepartsremoved, and

Figure 15 is an electric circuit diagram for the simplified control of atotalling wheel in addition or subtraction.

The differential driving-mechanism illustrated in Fig.- ures 1 and 2 ismounted on a driving shaft l. The planet wheels 2 and 3 of thedifferential can turn on a pin 4 which extends through the driving shaft1 and the ends of which are engaged in a supporting ring 5' whichsupports other planet wheels.A 3av and 3b. The planet wheels of thedifferential engage with the toothedV rims 6 and 7 of the bevel gears 8and 9 of the differential. The bevel gear 8 is provided with drivingteeth l0 engaging with the pinion` 11 of a mechanism to be driven. Thesaid teeth are arranged to engage with a number of other mechanisms tobe driven at the same time. The bevel gear 3 is provided with lockingteeth 12 and the Vbevel gear 9 is provided with locking teeth 13. A con;

trol member 14. rockably mounted on a supportingshaft 15 is providedwith a locking pawl :i6 which is adapted to be brought into engagementwith the locaing teeth 12 of the bevel gear 8, and. with a loing pawl 17which is the inoperative position.

is adapted to b'e brought into enagagement with the lock- Y gaged fromtheir corresponding looking teeth.` A'starting 'electromagnet 18attracts,when energised, Va plunger arm 19, which is Yprovided with abar 23 engaged inla fork 24 provided in the control member 14, whichrocks to the left andengages the locking pawl 17 in the vteeth 13 of thepassive bevel gear 9. A stop electromagnet k20 attracts, when energised,a plunger arm 19 which rocks'ithe Ycontrol member 14 to the right andengages the locking-pawl 16 in the locking teeth 12 Vofthe active bevelgearl8. Two springs 21 and 22 mounted o'n bevel gear 9.' If, forexample, the driven mechanism is locked or brakes the active bevel gear8 to the point of reducing its speed (which was twice that of thedriving shaft), the reaction of theY planet wheels on the bevel gear 9,forces the roller 29away from the teeth 13, the member 25 rocks and'thebevel gear 8 is no longer driven in a'determinate-mannerby thedrivingsha-ft;` In order to compensate for the'reaction of the drivenload 'Y Aduring operation on the roller 29 engaged in the locking asupport 31 act on the bar 23 and normally maintain Y v the controlmember in the inoperative position illustrated in Figure l, An auxiliarylocking device comprising the member 25 mounted freely on a fixed pin 30comprises a lever 26, which will be termed the active lever, because itis associated with the locking'teeth of the active bevel gear 8, and Yalever 27, which will be termed the passive lever, because it isassociated with the passive bevel gear 9. TheV lever 26 is provided witha rollerr28 illustrated in Figure l, which, is engaged in thelocking 7teeth 12 of the active bevel gear 8. The lever 27 is prog vided with aroller 29 illustrated out of engagement with the lockingV teeth 17 ofthe passive bevel gear 9.

' l The driving shaft 1 turns in the directionof the arrow F Vand drivesthe planet wheels of the differential inthis movement. The roller 28being engaged in the locking teeth12 of the active bevel gear 8,prevents the latter from turning. The planet wheels driven by theYdriving shaft engage on the one hand with the toothed rim 6 of the bevelgear 8, which is locked by the roller 28, and on the other hand with thetoothed rim 7 of the bevel gear 9, which is driven at a speedY ofYrotation twice the speed of rotationV of the driving shaft. v.By

the rotation of the bevel gear 9, the locking teeth 13V` of this kbevelgear urge the roller 29 out of engagement with the said teethr andthethrust of the teethY on the saidy roller, by rocking vthe member 25,maintainsthe Yoccupied by the control members in theV course oftheoperation of the device are illustrated in the diagrammatic'Figures 5 to10. The position of thecontrol memberin Figure 5 corresponds to thatofFigure ,1, which `g Starlingof the driving mechanism .'Whenthew'start'electromagnet 18 (Figure l) isnener'- gised, itcauses thelocking of thetbevel gear 9 as already bevel gear 8, which is thensetinV movement. The tooth Y explained. .The planet wheels 2, 3 whichrotate continuoursly about the axis of the driving shaft, engage withtheir teeth in the toothed rim 7 of the bevel gear 9, which is heldfast, and react on the teeth of the rim 61o'fthe 12av (Figures 41 and 6)Yof the teeth ,'12 forces ,the rollerV roller 29 engaged in the gapy11311 in the locking teeth 13 of the bevel gear 9, which is thuslocked. From this i 12 in movement, by acting on the roller 28, maintainthe instant, the energisation of the electromagnet 18 'may beVinterrupted to allow fthe spring 21 (Figure 1)to1return the pawl 17 tothe inoperative position. The resistduce through the planet wheels,reactions on the PaSSYe teeth of` th'e'fbevel 'gear 9 (Figure 8),.thelocking lever 26 has been made with a length L greater than the length lof the locking lever Y27. yOwing to the difference in the lengthrof thelevers, the roller V29 exerts on the locking teeth 113 a pressurestronger than the pressure exerted on the roller 28 by the locking teeth12. In addition, the locking levers are so disposed that, in relation tothe direction of rotation of the bevel gears, Vthe lever 27 is inabutment with-the teeth of thepassive bevel gear 9V.T A similar`condition is produced in the device illustrated in (Figurel-l, inwhichV thecontrol member 14a and the locking devicev 25a consist ofsliding members. VIn this arrangement, .the toothA .13C vof the bevelgear 9a abuts the roller-29a while the teeth 12C force the roller 28a inthe direction of the arrow E.

Stopping of the driven mechanism A -'l`o stop the bevelfgear 8 andV thusthe driven mechavthe pawl y16 (Figure-10j), a toothV gap 12rd is stoppedin 4an appropriate position to receive the roller 28, which engages inthe gap 12d due to the rocking of the member 25 under the action of vtheteetht13 of the vbevel gear 9, which forces the roller 29 outiofengagement. The pawl -16 can then kbe disengaged by'interruptionY of theenergisation of the stop electromagnet 20. Sincethe bevel gear 9 has4only to supply the elortnecessaryV to hold the roller 29 out ofengagement and does not drive the mechanism, the reactions ofthe planetwheels on the bevel gear 8 are reduced and cannot force the Vroller 28out of engagement. 'I'he Ydevice for actuating the control memberillustrated in Figure 3 is equivalent to that illustrated for Ythekcontrol of/atotalling wheel driving device in the aforesaid FrenchPatentV No. 527,463. Mention has al- ,ready been made of thedisadvantage of this arrangement, which requires-that the startVelectromagnet 18a `should be maintained in the energised conditionthroughoutthe time during which the mechanism coupled with Vtheactivebevel gear is to bedriven; .Figure 4 showsa control member `Ma'actu'atedbymeans of an electromagnetoperating with a polarisedblade. The Ycontrolmember is provided with aV soft-iron shank or blade 32 which extendsthrough anraperture 33'formed in a permanent magnet 34,51the north and.south poles of whichare marked N and S'res'pectively'. The blade 32 alsoextends throughan induction coil 35, and is maintained in the centralinoperative position by a resilient device not shown. .When anelectriccurrent is set up in the coil 35, the blade `is attracted eitherbythe north pole or by the south pole of thepermanent magnet, dependingupon the direction ofthe current in the'coil, and thus'eiects thestarting or stopping ofthe mechanism. A 'i When thedriving shaft Vlis,stopped-and Vwhen thedevice of Figure lis inoperative, andno lockingpawl is engaged (in contrast .to what is the case with-the deviceillustrated-in Figure 3), the position-of the auxiliary .locking deviceis indeterminate and the Astarting of the drivingshaftcan .bringaboutthe' involuntary starting of jthefmechanismcoupled with Vthe .activebevel gear of theV differential,v A

- Y.' AInorder `to obviate this disadvantage, a brake is-'pro- Vances ofthemechanism driven by the bevel gear 8 provided whichconsistsr(FiguresSxand l2)Y ofa springY 'blade 36,`one end of which is xed to aV xed bar'37.

The other end ofthe blade rubszon a portion of the memandere ber 25'so-as to maintain the said member, in the absence of any-other action, inthe position in which it is situated when the driving shaft is stopped.Thus, when the driving shaft of the device is ite-started the latterstarts again in the operative condition in which it was when the drivingshaft was stopped. A similar device is illusstrated in Figure l1, inwhich a spring 38 maintains the sliding member 25a in the position intowhich it has been brought. In another arrangement illustrated in Figure6, the member 25 is provided with a shank 38 whichr rocks between twomagnetised bars 40 and 41 and is .magnetically held against one bar orthe other depending upon the position into which it is brought under theaction of ythe locking teeth of the bevel gears on the rollers of thelocking levers.

Figure l2 illustrates in transverse section an accumulating mechanismfor a record card accounting or statistical machine. eference may bemade by way of indication to the French patent applied for on January 8,1936, No. 811,724, and to the first addition to the said patent, appliedfor on February 12, 1936 and granted under the No. 47,642, in whichthere is shown an example of the use of accumulating mechanisms. Anaccumulating unit normally comprises 12 totalling wheels, each totallingwheel being coupled with a rotary distributor switch and with a systemof cam-controlled electric contacts to close and open contactscontrolling the carry-over circuits. ln order to deal with numberscomprising more than l2 digits, electrical connections may beestablished to combine a number of accumulators, and to deal withnumbers comprising only a few digits the wheels of one accumulator maybe used in groups of three or multipies or three wheels. In theaccumulating mechanism illustrated in Figure 12, the mechanism by which.the totalling wheels are driven is that illustrated in detail in Figures1 and 2.

ln the following description, identical members will bedesignated by thesame references. The driving shaft 1 supports differential drivingmechanisms comprising a bevel gear provided with teeth li meshing with apinion 11 of insulating material, which is arranged to rotate freely ona pin 47. The said pinion supports the contacts 42 and 43 of a rotaryswitch. When the pinion is driven the said contacts travel successivelyover contact studs Si? to 59, which are thus successively electricallyconnected to a contact segment The contact studs and the Contact segmentof each switch are connected to output studs PX, P1, P2, P9, P connectedto the utilisation circuits of the machine (not shown). The Contact`studs, the contact segments and the connections to the output studs areconstitutcd by printed circuits on insulating plates 45, 46 mounted onsupporting bars iS-49, each insulating plate bearing the printedcircuits of one switch on each face. The control members 11i are mountedon the supporting shaft and actuated by start and stop electromagnets 18and 2i). The auxiliary locking devices comprising the members 2.5 aremounted on the shaft 3d. There also meshes with the teeth 10 a toothedpinion mounted freely on a shaft 62. Keyed on each pinion 6@ is acarryover c-am 61 which, when driven, pushes at each revolution acarry-over contact lever 63. Since the operation of the carry-overcircuits of accumulators is known to the person skilled in the art, itwill not be described. The supporting shafts 47, 3u, 15 and 62 aresupported in the accumulator by side plates 72 and 73 (Figures 12 and13). The side plates are connected by cross bars 64 and 65 andsupporting bars 66, 67, 63, which support the stop electromagnets 243,the start electromagnets 18 and the insulating supports 74 of thecarry-over contact blades respectively. The spring blades Se form brakesfor the members 25. The said bars also form cross members `between theside plates of the accumulator. Keyed ontlie driving shaft 1 is a pinion69 (Figure l3)driven a number of accumulatore.' Keyed on the pinion 77meshing with the pinion 69 is aicam 78 which, at each revolution,actuates'the bars 79 for resetting the carryover contacts by actingonthe lever 1S through a roller 81 which is constantly applied againstthe can178 under the action of a return spring 82. For the sake ofclarity, the bars y37, 48y and 64 (Figure 12) are not shown in Figurel4.

An accumulator provided with driving devices. designed in accordancewith the invention may be employed directly for addition and forsubtraction.

Figure 15 is a very simpliiied diagram illustrating the principle of theelectric' circuits provided for this mode of use in a machine controlledby punched vrecord cards. The record cards are successively fedVinto'the machine and pass in the direction of the arrow D under scanningbrushes disposed in rows. The irst row, calledl the upper brush set BS,scans the control perforations indicating the operation to be carriedout on values Iwhich are thereafter analysed during the passage of thecard below the brushes of the lower brush set Bl. In the punched cardpartly illustrated in Figure 15, record perforations are formed inhorizontal rows of value 9 to 0, 11 and 12 and in vertical columns. Eachcolumn thus comprising the positions for the perforations of value 9 to0, ll. and 12 is scanned by a brush. All the perforations of like valueare simultaneously scanned. The perforations for the number 2147 areindicated on the card in Figure 15.

A perforationv S in the row ovalue 12 may be utilized to control thesubtraction of this number from a number` already introduced intoanaccumulator. The arrangement of the contacts illustratedA in solidlines'corresponds to the arrangementfor the introductionY of a numberduring addition. A manually operable contact 91 permtis, when closed, ofeffecting the introduction of a number during subtraction after thescanning of' a perforation S during the passage of a card under theupper brush set. The contact 91 beingshown open, the introduction willbe made for the purpose of addition. Thebasic circuits have beenillustrated only for the brush 92 of the upper brush setBS and only forthe brush 93 of the lower brush set BI. The operation of the circuitsfor the brushes scanning the other columns of perforations indicated issimilar. For the addition, the passage of a perforation 4 under thebrush 93 establishes the following circuit: from the positive pole ofthe curren source, through the line 94, the contact 95 closed by the cam95e during theV passage of the record positions 9 to 0 of the card belowthe scanning brush set BI, through the contact' brush 96, the contactroller 97 and the perforation 4, the current ows through the brush 93,the line 98, the contact 99 and the start electromagnet 1S which isenergised, the line 190 and the negative pole of the current source. Theenergisation of the start electromagnet at the instant of the scanningof the perforation 4 of the card starts vthe corresponding totallingwheel. This wheelY continues to rotate. synchronously @with the movementof the card until theY instant when the-row 0 of the card travels underthe analysing brush. set. At this instant, the said wheel like all theother totalling wheels started during the scanning of a card, is stoppedby the clossing of the cam cont-act 101', which establishes the'`following circuit: positive pole', closed cam contact` 101, contact102, line 103, Contact 104, ystop electromagnet 20, line 100, negativepole of the current source. The totalling wheel started by the scanningof the perforation 4-has at this instantrecorded the value 4 in the tensorder oftlie accumulator by turning the corresponding switch throughfour studs. For the subtraction, the process is'dilerent. It is knownthat Vit is possible to subtract one number from a larger number by theaddition of the complement to 9 of each kdigit to-be subtracted and byeffecting a carry-overfor correction of ther result. It is known' toeffect such an addition of the complement inpunched-card. machines byrotating through pinions-71 and 75 bythe shaft 76,- which drives 75thezfotalling. wheelsrat rheinstanpwhemthefrow ofI Per,

forationpos-itions of thevalue 9.of the card passes below the scanningbrushes and to stop each ,wheell as Va result of the scanningof Yaperforation in a corresponding columnjof'theY card.V AnV accumulatorYin` which', the wheels are provided withthe Ydriving mechanismaccordingto the invention lends itself with' advantage to. the perfomance ofthesubtraction in th'e'aforesaid manner. An

Yaccumulator having six totalling wheels will bejconsidered,1 in whichthe number-42595 is alreadysituated.V

For Vsubtracrrting the Vnumber 2147 `from 'thisnumbeig it is necessaryto add to"'42595A the Vcompleitnentto 9 of V 2147. "For `siX totallingwheels, this complement is 997,852.` The result of this addition is1,040,447. YThis result is corrected 4by introducing into th units orderthe carry-over whichV would ktake up a position in a seventh totallingwheel. for the millions order. AThe corrected result obtained is 40,448V

I,}-997,852 (l) ,040,447 l In accordance with the diagram of Figure V15,the digit Y up Vthe position indicated in broken llines inthe diagram.

Theelectromagnet 109 is maintainedY energisedV by the contact 110through the cam contact 111. Means not shown Vare provided to preventthe scanning of a control perforation in the following cardrfrommodifyingr the Y control circuits established for the preceding card.During the Vpassage belowY the brush set BI ofthe row of perforationkpositions for the value 9 in the'card 90, the following circuitis'established': positive pole, cam con-A tact 112 (this contactclosesronly at thepoint 9), contact 113, line 103, Ycontact 114, 'startelectrom-ag'net 18, return to negative. vThe six Wheels'o'f vtheaccumulator whichf'are allocated to the'subtraction start at the point 9except those forwhich Va perforation 9 is scanned.Av YIn Vthis case, thesimultaneous energisation'of the two electromagnets and 18 controlling atotalling wheel, has nov effect on the member controllingV this wheel.Thescanning of the perforatior'rlr in the card which is then effected bythe brush 93 energises the electromagnet 20, which stops theitotallingwheel of the tens order which has at this instant adyancedY byve units.Before 'the' instant when theV row of positions for the perforationsof'the value 0 in the card passes below theV brushes, the cam 111interruptsthe holding of the relay 109'the contact blades 105 to 108 ofwhich return to the position indi:l

cated in solid lines. .All the stop electromagnets 20 Vare energised bythe'ca'm Contact 101, which closes at the point 0, andthewheelswhich'have not been stopped by the scanning of a perforationsituated Vin, aV row of value between 9 and O'are stopped.

, A'special kconnection feeds'Y o'the units'V order wheel (as alreadystated) the carry-over emanating fronrthe highest'order ofthe groupioftotalling wheels;

Y The wheel'of Vthe tens orderYV of the accumulator, advanced by fiveunits, Vrepresents the tens digit of the re- Vsult and has produced thetransmission Vof a carry-over, f j

. The embodiment fdescribed by way `of example isin Vno Vway limitativeand the invention is applicable notably to selector-distributorsemployed in automatic. telephony nisms depending upon the circumstancesandapplications without departing from the spirit ofY theinvention.v f*l LVA differential-driving mechanism comprisingtwo bevel gears mountedrotatable'on arcommon'shaflt, 'one or more planet/wheels, constantlyengaged with said two bevelV gears, said planet wheelorj wheels beingdriven with a continuous rotational movement about ythe axis of saidshaft, means connecting one bevel gear withone or more mechanisms'to'bedriven,` first locking means comprising for each bevel ygear at leastone set of locking teeth and a lockingrp'awl normallyheld out of en*-gagement with the'said lockingteeth, control means for said pawlcomprising an electromagnet so Ydisposed that the temporary energisationof'said eleotromagnet brings said pawl into engagement with the lockingteeth of the corresponding bevel gear lockingsaid bevel gear, said rstlocking means being adapted to lock one'bevel gear orrthe other so thatthe unlocked bevel gear is rotated by the movement of the planet wheelor wheels, said control means being so arranged that the simultaneousenergisation of the twoelectromagnets has no elfect on said pawls, andsecond locking means adapted to maintain the locked bevel gear in itslocked position under the action of the movement of the locking teeth ofthe driven bevel gear. Y

2. A differential driving mechanism comprising [two bevel gears mountedrotatable on a common shaft, one or more planet'whcels constantlyengaged with said two bevel gears, said planet wheel or wheels beingdriven with a continuous rotational movement about the axis of saidshaft, means connecting one bevel gear with one or more mechanisms to bedriven, irst locking means comprising for each bevel gear at least oneset of Vlocking teeth and a locking pawl normally heldV out ofengagement with said locking teeth, control means for said pawlcompris-v ingpan electromagnet so disposed that the temporaryenergisation of said electromagnet brings said pawl Vinto engagementwith the locking teeth of the corresponding bevel gear and lock saidbevel gear, the unlocked bevel gear being rotated by the movement of theplanet wheel or wheels, the lockingpawls of the bevel gears beingrigidly fast with oneranotherV and mounted to rock about a fixed axis, aspring device normally maintaining said pawls out of engagement with thelocking teeth of the y driven -bevel gear.

3; A Vdifferential driving mechanism comprising Vtwo bevel gears mountedrotatable on a common shaft, one or more planet wheels constantlyengaged with said two bevel gears, said planet wheel or wheels beingdriven with a continuous rotational movement about the axis of saidshaft, means connecting one bevel gear with one or more mechanisms to bedriven, first locking means comprising for each bevel gear at least oneset of locking teeth and a locking pawl normally held out of engagementwith said locking teeth, control meansifor'said pawl comprising anelectromagnet so disposed that the temporary energisation of saidelectromagnet brings said pawlinto engagement with` the locking teethvof the corresponding and to all like devices, and'any modicationsintheform and arrangementof the parts may be made in the mechav bevelVgear, locking said bevel gear, the unlocked bevel gear being rotated bythe movement of the'planet wheels, the'locking Vpawls Vbeing rigidlyfast with one another on a support sliding along an'axis and disposedsothat said locking pawls can not be simultaneouslyV brought inengagement into the locking teeth of the bevel gears,

a spring device normallymaintains the said pawls out'of p 4. Adilferential driving mechanism comprising-,two bevel gearsmountedrotatable on -a common 's haft, one

or more planet wheels, constantly engaged with the said two bevel gears,said planet wheel or wheels being driven with a continuous rotationalmovement about the axis of said shaft, means connecting one bevel gearwith one or more mechanisms to be driven, first locking means comprisingfor each bevel gear at least one set of locking teeth and a locking pawlnormally held out of engagement with said teeth, control means for saidpawl comprising an electromagnet so disposed that the temporaryenergisation of said electromagnet brings said pawl into engagement withthe locking teeth of the corresponding bevel gear, locking said bevelgear, the unlocked bevel gear being rotated by the movement of theplanet wheel or wheels, the locking pawls being fast with a -bladeadapted to rock about a `fixed axis and situated within an inductioncoil disposed between the arms of a permanent magnet so that when acurrent is passing through the induction coil in one direction or in theother the blade is attracted towards one arm of the permanent magnet orthe other and one locking pawl or the other is brought into engagementwith the locking teeth of the corresponding bevel gear, thus starting orstopping the driven mechanism in accordance with the direction of thecurrent through the induction coil, and second locking means adapted tomaintain the locked bevel gear in its locked position under the actionof the movement of the locking teeth of the driven bevel gear.

References Cited in the le of this patent UNITED STATES PATENTS2,078,161 Rietsch Apr. 20, 1937 2,444,566 Hennessy et al July 6, 19482,558,953 Henninger et al. July 3, 1951 2,770,145 Stibitz Nov. 13, 1956

